Many substances which are considered contaminants, such as volatile organic compounds (VOCs), are widely used as an indispensable part of many industrial processes. During such uses, it is inevitable that articles or process fluids become contaminated with the VOCs. In recent decades, heightened awareness of the deleterious effects of these compounds has led to the realization that efficient, effective devices or processes must be developed for treating such articles prior to reuse or such fluids prior to discharge into the environment. With regard to the latter, exemplary treatment systems can be found in U.S. Pat. No. 5,552,051 to Wang et al. for a soil washing system that removes VOCs from wash water and U.S. Pat. No. 5,348,588 to Winston covering a system for the removal of various contaminants, including VOCs, from water used to wash electronic circuit assemblies.
A particular area of concern is with the washing of articles contaminated with VOCs and the further treatment of the water used to clean such articles. Examples of such articles include towels used for cleaning solvents from printing presses ("print towels"), shop towels, floor mats, or uniforms worn by workers in industrial locations. As should be appreciated, the extensive use and reuse of such items in a wide variety of industries creates a large quantity of contaminated articles that must regularly be washed.
During the conventional wash process, the articles are saturated with fresh water and are thoroughly washed with the goal of removing substantially all contaminants present. Although such washing is effective for removing a wide variety of contaminants from the articles (usually cleaning compounds, such as surfactants), it should be appreciated that the wash process simply transfers the contaminants, including VOCs, to the wash water. Thus, the contaminants are free to re-associate with the articles being washed. This of course reduces the effectiveness of the wash process.
One solution is to continuously discharge the contaminant laden water and replacing it with potable water, much like is done in home washing machines. While providing effective cleaning action, this approach disadvantageously results in a significant waste of important natural resources and also introduces further inefficiency into the wash process. Moreover, the discharged wash water will ultimately require treatment prior to release to comply with various governmental regulations seeking to ensure that the deleterious effects of VOCs, etc. upon the environment are minimized. Separate treatment processes further hinder the efficiency of the wash process and require significant operator intervention and monitoring to ensure that the process is effectively removing contaminants. Indeed, the presently known treatment systems use flotation principles and filtering to remove grease, oils, and heavy metals, but such treatment methods generally simply do not effect a significant reduction in the VOC levels in the wash water.
Therefore, a need is identified for an apparatus for treating a process fluid that is used to remove contaminants from articles, such as water used to wash print towels contaminated with VOCs. To reduce the consumption of water and enhance process efficiency, the apparatus would circulate and treat the wash water to remove contaminants, while at the same time monitoring the contaminant level and continuing the wash process. Automatic process controls would actuate the apparatus to continuously recirculate the wash water until an acceptable level of cleaning is reached. The wash water could then be discharged to the environment.